"Parcel media" refers to playing music, movies, webpages, & more on your land parcel(s) in Second Life. Once you learn how, it's easy to do.
We have a helpful selection of articles in our Knowledge Base detailing how you can play parcel media. In particular, see:
You can also watch video tutorials like this:
What will play?
Any format that QuickTime supports should work inworld, as well as standard webpages. So a good general rule is to try to play URLs in QuickTime Player or your web browser.
Play media externally
Media streams used inworld can also be played in external players, depending on what formats they support. iTunes and Winamp for audio, and QuickTime Player and VLC for video are among the more popular ones. Since these are 3rd-party programs, Linden Lab doesn't support them, but here's basically how to make media streams work.
Once you have a media URL (e.g., xxxx which is an Internet radio stream):
iTunes runs on Windows and Mac.
Winamp only runs on Windows.
QuickTime runs on Windows and Mac.
VLC runs on Windows, Mac, and Linux.